The present invention relates to x-ray imaging, and more particularly, to digital subtraction for an x-ray imaging roadmap application.
Digital subtraction is a common procedure for many medical imaging applications. For example, digital subtraction of x-ray images is commonly used for a roadmap application in coronary intervention or angioplasty procedures. In such a roadmap application, since vessels cannot be seen clearly in traditional x-ray images, a contrast media is injected into the vessels to highlight the vessels. This results in a mask image with the vessels highlighted. The contrast media is then flushed away, and during the intervention procedure, a guide wire is inserted into the vessels. To highlight the guide wire's location within the vessels, the mask image is subtracted from the current image that shows the presence of the guide wire. The final subtraction result (Isub) is an image of the guide-wire overlaid with the vessels to act as a roadmap to help a physician position the guidewire.
However, since the imaging noise in the mask image and imaging noise in the current image are independent of each other, the noise in the subtraction result is greater than in either of the two input images (i.e., mask image and current image). Accordingly, the signal to noise ratio of both of input images is better than that of the subtraction result. Thus, an improved subtraction procedure for roadmap applications that achieves a subtraction result with a better signal to noise ratio is desirable.